As for a dislocation free, silicon single crystal grown by pulling from a silicon melt by means of a CZ method or a FZ method, it has been hitherto known that swirl defects and D-defects (in case of FZ crystal) or phenomena such as ring-shaped OSF defects, abnormal oxide precipitation, and degradation in breakdown voltage of an oxide film (in case of CZ crystal) occur in the course of heat treatment process of a wafer, depending upon the crystal pulling condition or crystal pulling apparatus condition as described by Takao Abe, in Applied Physics, 59 (1990), p. 272. Any of these defects and the phenomena affect quality of a silicon wafer used as a substrate for highly integrated ICs.
Distribution and density of these defects in a silicon single crystal grown from a melt largely depend on the pulling condition of the crystal. Therefore, it has been considered that occurrence of these defects is determined at the time of crystal pulling. Therefore, these crystal defects are named generically "crystal defects determined during the crystal growth to occur" or "grown-in defects."
The grown-in defects provide a ring-shaped or disk-shaped macroscopic distribution in a section perpendicular to the growth axis of the crystal. It has been an important subject of research in the pulling technique of CZ and FZ silicon single crystals for a long time to elucidate the generation mechanism of the macroscopic shape.
As for such grown-in defects, it has been a dominant view that point defects such as interstitial atoms and atom vacancies taken into the crystal from the crystal growth interface during the crystal growth become thermally superfluous, agglomerate, and form nuclei of the grown-in defects as described by Takao Abe, in "Applied Physics," 59 (1990), p. 272. Therefore, it has been considered that the peculiar distribution shape of grown-in defects can be explained in terms of diffusion of interstitial atoms and atom vacancies and reaction between interstitial atoms and atom vacancies in the silicon crystal in the course of crystal pulling. (See V. V. Vronkov, J. Cryst. Growth, 59 (1982), p. 625; T. Y. Tan and U. Gosel, Appl. Phys. A37 (1985), p. 1; and W. Wijiaranakula, J. Electrochem. Soc., 139 (1992), p. 604.) In the existing circumstances, however, the diffusion equation of interstitial atoms and atom vacancies capable of determining on the basis of crystal growth condition, the shape in distribution of grown-in defects observed in CZ and FZ silicon crystals has not yet been established as pointed out by K. Sumino, in Materials Science Forum, Vol. 105-110 (1992) Pt. 1, pp. 139-160, EDs. Zs Kajcsos & Cs Szeles, Trans. Tech. Publications.